Crystalline polyketones, particularly polyaryletherketones as described in, for example, U.S. Pat. Nos. 3,953,400; 3,441,538 and 4,010,147 are known to exhibit a superior combination of properties, such as high use temperatures, thermal and photochemical stability, and resistance to attack by solvents. These properties are due primarily to the high melting points, generally about 250.degree. C. and higher, and to the crystalline nature of these polymers.
European Patent Application Publication No. 0148633, published Jul. 17, 1985 describes a process for preparing a high molecular weight crystalline polyaryletherketone by forming a polyketal and then converting the polyketal to a polyaryletherketone. The conversion of the polyketals to the polyaryletherketones is described, as conducted in the presence of water and an acid under heterogeneous or homogeneous conditions, on page 43.
Generally, heterogeneous conversion is carried out by treating the polyketal with an excess of water, optionally, in the presence of an organic liquid and dilute acid catalyst. The polyketal is preferably in the form of finely divided particles or a film, either in solid form or in the melt, which are substantially insoluble under the reaction conditions. The weight ratio of water to polymer is preferably from about 1 to about 100, although greater amounts of water can be used. The acid catalyst is used preferably at concentrations of from 0.0001 to about 20 weight percent of the water present and, most preferably, from about 0.005 to about 2 weight percent. Suitable acid catalysts include strong mineral acids, such as hydrochloric acid, nitric acid, fluorosulfonic acid, sulfuric acid and the like, and strong organic acids, such as p-toluenesulfonic acid, trifluoromethane sulfonic acid, and the like.